sorry if it's a very basic question, but i can't figure it out myself...
the attached waveforms were captured while playing back an 1khz 0dbfs sine with 8x oversampling (fs=44.1khz). the i/v stage is an 8 ohm resistor to ground (for this measurement).
what i was expecting is a relatively pure staircase pattern. i assume there is some high frequency dirt on the signal. do you guys have any idea?